This invention relates generally to electronically steered antennas and more particularly to apparatus for controlling a plurality of digital phase shifters in antenna arrays.
It is sometimes desired to control the direction of a single beam from a phased array antenna by an electronic beam steering technique rather than to use a multi-beam technique. Thus, if an electronic beam steering technique is used, a single beam may be controlled so that the centerline of such beam is directed toward almost any desired point within a field of view; on the other hand, if a multi-beam technique is used, the direction of each beam is fixed within a field of view. It follows then that an electronic beam steering technique permits better aiming of a single beam.
Using any known electronic steering technique, the time taken to complete an operational cycle, i.e. the time required to change the direction of a beam, is in the order of 100 microseconds. Even though the time required to switch an individual control element, say a digital phase shifter, is in the order of tens of nanoseconds, any known architecture for electronic steering of a beam from a phased array antenna using hundreds of digital phase shifters requires a settling time in the order of 100 microseconds. Further, if each digital phase shifter incorporates a number of bits (say 5 to control the phase of radio frequency energy to about 10.degree.), any known architecture requires at least one (and probably two) separate control wires for each bit. Obviously, the total number of control wires in any practical application using hundreds of digital phase shifters is in the thousands.